So some things I've noticed/wanted to put out there from the trailer:

1. On the new magic blade - The sword has two forms, similar to the original monado. Its closed form (visible at the end of the trailer), and its open form.
2. Something to also note from the above scene/screenshot is that the contraption (perhaps a helmet?) on the protagonist's back is either lit up or on fire, which is interesting because it appears to be hollow normally (you can see light passing through it from its presumably open top).
3. On Elysium - Obviously Elysium is a major fixture for the game (considering it's mentioned in the first line of the trailer). And we know how Monolithsoft loves their mythology references. Elysium refers to the Elysian Fields, an afterlife of sorts for heroes, gods, and others chosen by the gods. It's suggested to be a series of islands at the Western end of the world, at least in some tellings. And for Xenoblade 2, we know that "Elysium of the blue sky" is the name of the game's main theme (part 2, at least). That suggests that Elysium could be a floating island, or some mythical airship or Bionis-esque creature, or the tree shown at the end of the trailer.
4. The game (at least in part) takes place on top of a living creature. The opening shot pans left to reveal this mountain, which isn't a mountain at all - but the neck and head of a massive creature that turns slowly to the right before the trailer cuts to the next shot. Considering that we know that Shulk recreated the entire galaxy (if not entire universe) with Alvis at the end of Xenoblade Chronicles, it's possible that this takes place on a completely different world. Regardless, it's likely that because the symbiosis of massive creatures big enough for smaller human-like species to live on is all Shulk knows, any world Shulk creates would've been made in that vein.

I know people have also compared the aesthetic of the one female character's outfit to characters from XCX, but I think it's also fairly similar to some Machina armor sets and the Monado aesthetic. I also think there's a small possibility that this character is the "soul" or manifestation of the monado that the male protagonist is wielding. There's no proof, obviously, but the glowing headpiece and earrings, while standing in the midst of flames and smiling, in front of a nondescript background (though there does seem to be a lightning flash)... it makes me question whether she's really real.